Enhanced Noninvasive Collagen Remodeling

ABSTRACT

A method and apparatus for treatment of skin or other tissue, using a source of thermal, electromagnetic radiation, electrical current, ultrasonic, mechanical or other type of energy, to cause minimally-invasive thermally-mediated effects in skin or other tissue which stimulates a wound-healing response, in conjunction with topical agents or other wound healing compositions, for application on the skin or other tissue which accelerate collagenesis, such as in response to wound healing. The dosage and time period of application of the compositions are adjusted to prevent external or surface tissue damage.

FIELD OF THE INVENTION

This invention is related to the controlled delivery of photothermal orother type of energy for treatment of biological or other tissue, andmore specifically, a method, system and kit for causing a subdermalwound such that upon application of a growth factor, collagenesis andfurther repair and healing improvement of tissue is accelerated.

BACKGROUND OF THE INVENTION

Collagen is the single most abundant animal protein in mammals,accounting for up to 30% of all proteins. The collagen molecule, afterbeing secreted by the fibroblast cell, assembles into characteristicfibers responsible for the functional integrity of tissues making upmost organs in the body. The skin is the largest organ of the bodyoccupying the greatest surface area within the human body. As ageadvances and as a result of other noxious stimuli, such as the increasedconcentration of the ultraviolet part of the electromagnetic spectrum asradiated from the sun, structural integrity and elasticity of skindiminishes.

Crosslinks between adjacent molecules are a prerequisite for thisintegrity of the collagen fibers to withstand the physical stresses towhich they are exposed. A variety of human conditions, normal andpathological, involve the ability of tissues to repair and regeneratetheir collagenous framework. In the human, 13 collagen types have beenidentified. Of the different identifiable types, type I is the mostabundant in skin where it makes up 80 to 90% of the total collagenconnective tissue. This type of collagen, however, is less dynamic inthe full-grown individual than its counterparts in which collagen isinvolved in active remodeling. In this case the normal collagensynthesizing activities in skin is relatively quiescent exhibiting slow,almost negligible, turnover.

The extra-cellular matrix of the various connective tissues, such asskin, consists of complex macromolecules, collagen, elastin andglycosaminoglycans (GAGs). The biosynthesis of these macromoleculesinvolves several specific reactions that are often under stringentenzymatic control. The net accumulation of connective tissues is thus,dependent upon the precise balance between the synthesis and thedegradation of the connective tissue components.

Previous disclosures, such as U.S. Pat. No. 4,976,799 and No. 5,137,539have described methods and apparatus for achieving controlled shrinkageof collagen tissue. These prior inventions have applications to collagenshrinkage in many parts of the body and describe specific references tothe cosmetic and therapeutic contraction of collagen connective tissuewithin the skin. In the early 1980's it was found that by matchingappropriate laser exposure parameters with these conditions, one had anovel process for the nondestructive thermal modification of collagenconnective tissue within the human body to provide beneficial changes.The first clinical application of the process was for thenon-destructive modification of the radius of curvature of the cornea ofthe eye to correct refractive errors, such as myopia, hyperopia,astigmatism and presbyopia. New studies of this process for thepreviously unobtainable tightening of the tympanic membrane or ear drumfor one type of deafness have been made.

In addition to addressing the traditional method of collagen shrinkagewherein the ambient temperature is elevated within the target tissue byabout 23 degrees Celsius, the “thermal shrinkage temperature” ofcollagen, T_(s), a novel method for obtaining controlled contraction ofcollagen at a much lower temperature has been developed. Evidence existsto elevate the mechanical role played by the GAGs in the collagenousmatrix. Removing or altering these interstitial chemicals by enzymes orother reagents as disclosed in U.S. Pat. No. 5,304,169 considerablyweakens the connective tissue integrity and influences the thermaltransformation temperature (T). Shrinkage temperature may be defined,therefore, as the specific point at which disruptive tendencies exceedthe cohesive forces in this tissue. This temperature, thus, makes thisan actual measurement of the stability of the collagen bearing tissueexpressed in thermal units.

The cause of wrinkles around the eyelids, mouth and lips ismultifactorial: photodamage, smoking and muscular activity such assquinting and smiling all contribute. The end result is a general lossof elasticity, which is a textural skin condition as opposed to a skinredundancy or excess of skin tissue. The surgical injection ofreconstituted collagen is commonly used in order to flatten the periorallines. While oculoplastic surgeons may treat this problem around the eyeinappropriately by blepharoplasty, it has been observed that eventransconjunctival blepharoplasty for removal of prolapsed retrobulbarfat fails to address the fine periocular lines or wrinkles. Untilrecently, the main approach to treating these blemishes has beenchemical peeling by means of trichloroacetic acid or phenol.Complications of chemical peels may include hypopigmentation, scarring,cicatricial ectropion and incomplete removal of the wrinkles.

Many patients are acutely aware of these cosmetic blemishes as evidencedby the large quantity of money spent each year in the U.S. and abroadupon home and spa remedies for a more youthful appearance. With theadvent of laser technology as an alternative to chemical peels ordermabrasion, dermal ablation techniques with both the conventionalcarbon dioxide lasers and the high energy, short duration pulse waveformCO2 lasers, high tech solutions appear to provide substantial benefitsto patients.

CO2 laser resurfacing is not a new technique. CO2 lasers have been usedfor several years, but regular continuous wave CO2 lasers can causescarring due to the tissue destruction caused as heat as conducted toadjacent tissue. Even superpulse CO2 lasers produce excessive thermaldamage. The Ultrapulse CO2 laser introduced by Coherent, Inc. is anattempt to assuage these drawbacks by offering a high energy, shortduration pulse waveform limiting the damage to less than 50 micronsallowing a char-free, layer by layer vaporization of the skin tissue.

All of the foregoing procedures depend for their success upon primarydamage and the reparative potential induced by the inflammatory processin the tissue. Associated with inflammation are, of course, the fourcardinal signs of inflammation of rubor (hyperemia), calor (thermalresponse), dolor (pain), and tumor or edema or swelling. Coincident withthese manifestations is the risk of reduced resistance to infection. Onemust not forget that these collateral effects accompany a cosmeticenhancement procedure and, for the most part, are not associated with atherapeutic procedure. Therefore, the development of a more efficaciousmethod would be beneficial in this regard.

Various undesirable skin conditions would be improved if the collagenunderlying the region of the condition could safely be improved withoutdamage to the overlying region. Wrinkles related to photodamage and acnescars are example of such conditions.

U.S. Pat. Nos. 4,976,709, 5,137,530, 5,304,169, 5,374,265, 5,484,432issued to Sand, disclose a method and apparatus for controlled thermalshrinkage of collagen fibers in the cornea using light at wavelengthsbetween 1.8 and 2.55 microns. However strong absorption of the laserenergy by water limits the penetration depth to the most superficiallayers of skin.

The CoolTouch (trademark) 130 laser system by CoolTouch Corp of Auburn,Calif., was first introduced at the Beverly Hills Eyelid Symposium in1995. It utilizes a laser at a wavelength of 1.32 microns to causethermally mediated skin treatment. In this device the treatment energyis targeted at the surface of the skin with in depth optical heating ofthe epidermis, papillary dermis, and upper reticular dermis. The energyis primarily absorbed in tissue water with a skin absorption coefficientof 1.4 cm-1, corresponding to an absorption depth of 0.71 cm. Scatteringof the 1.32 micron wavelength light by skin microstructures alters thedistribution of light from an exponential attenuation to a more complexdistribution, which has much faster attenuation approximating anabsorption depth of 0.1 cm. Most of the energy is absorbed in the first250 microns of tissue. To prevent overheating of the epidermis pulsedcryogen spray precooling is used. U.S. Pat. No. 5,814,040, issued Sep.29, 1998, describes a dynamic cooling method utilizing pulsed cryogenspray precooling. Skin treated with this device has improved texture anda reduction in wrinkles and scarring due to the long term renewal ofdermal collagen without significant skin surface wounding.

U.S. Pat. No. 5,810,801 teaches a method and apparatus for treating awrinkle in skin by targeting tissue at a level between 100 microns and1.2 millimeters below the surface, to thermally injure collagen withouterythema, by using light at wavelengths between 1.3 and 1.8 microns. Theparameters of the invention are such that the radiation is maximallyabsorbed in the targeted region. The invention offers a detaileddescription of targeting the 100 micron to 1.2 mm region by utilizationof a lens to focus the treatment energy to a depth of 750 microns belowthe surface. Because of the high scattering and absorption coefficients,precooling is utilized to prevent excess heat build up in the epidermiswhen targeting the region of 100 microns to 1.2 mm below the surface.The wavelength range of use is 1.3 microns to 1.8 microns in order toavoid the wavelength range of Sand. However the wavelength range of 1.4to 1.54 microns and the range between 2.06 and 2.2 microns haveidentical effective attenuation coefficients in skin. Also the rangefrom 1.15 to 1.32 microns has a fairly uniform effective attenuationcoefficient in skin of about 6 to 7 cm⁻¹. The effective attenuationlength in skin for the range of wavelengths of 1.3 to 1.8 microns variesfrom 6 cm-1 at 1.3 microns to 52 cm-1 microns, corresponding topenetration depths in skin of 200 microns to 2 millimeters. Specificlaser and cooling parameters are selected so as to avoid erythema andachieve improvement in wrinkles as the long term result of a newcollagen formation following treatment.

Kelly et al, report improvement in skin due to collagen remodeling aftertreatments with an Nd:YAG laser at 1.32 microns and cryogen sprayprecooling. In this case the method was designed to provide a series oftreatments with parameters selected to produce erythema and mild edema,with some improvement in facial rhytids several months following aseries of treatments. However, there is a risk of pigmentary change ortransient pitted scarring because of the high fluence level of thelaser, greater than 30 joules per square centimeter in 20 millisecondexposures, and the high level of pulse cryogen cooling.

Mucini et al. reported effective dermal remodeling using a 980 nm diodelaser with a spherical handpiece which focused irradiation into thedermis avoiding the high scattering and absorption characteristic oflonger wavelengths. The device requires a small lens of a fewmillimeters in contact with skin and results in a slow procedure whenused for facial areas.

Ross et al., reported the use of an Erbium:YAG laser operating at awavelength of 1.54 microns fired in a multiple pulsed mode has beendescribed for eliciting changes in photodamaged skin. A chilled lens incontact with skin at the treatment site was used in an attempt to sparethe epidermis. Treatment occurred during a period of several secondswith a sequence of cooling and heating with the laser and handpiece. At1.54 microns the optical penetration depth 0.55 mm and the authorsreported that the surface must be chilled before the laser exposurerequiring a complex method of cooling and laser exposure. The authorsstate that a more superficial thermal injury may be needed than could beachieved, and that there are increased patient risks because it woulddemand more accurate and precise control of heating and cooling.

Bjerring et al, reported the use of a visible light laser, operating at585 nm wavelength, to initiate collagenesis following interaction oflaser energy with small blood vessels in skin.

Other methods of creating subepidermal wounding may utilize electricalcurrent, ultrasonic energy or non-coherent light sources. In all ofthese methods, including those using lasers, collagen remodeling is along-term minimal response to the application of energy. Since theobjective is a non-invasive or minimally invasive procedure thestimulation of collagenesis must be below the threshold for creating anopen wound, resulting in a minimal treatment.

U.S. Pat. No. 5,599,788 describes a method of producing recombinanttransforming growth factor .beta.-induced H3 protein and the use of thisprotein to accelerate wound healing. The protein is applied directly toa wound or is used to promote adhesion and spreading of dermalfibroblasts to a solid support such as a nylon mesh which is thenapplied to the wound.

It is heretofore unknown to combine the adverse effect caused byexcessive photothermal, mechanical or other type of energy applied toskin or other tissue coupled with a topical or other administration ofgrowth factor(s) or wound healing factor(s) in order to amplify thenatural stimulation of growth or collagenesis caused by the wound.

OBJECTS AND ADVANTAGES OF THE PRESENT INVENTION

The object of this invention is to provide a method and device forimproving skin by treating layers of skin without damaging the surfaceor deep skin layers. It is another object of this invention to provide amethod and device for improving acne scars or photodamaged skin withoutcausing a surface injury to skin. It is another object of this inventionto provide a method and device for accelerating the collagenesis aftertreating skin without damaging the surface of skin.

It is yet a further advantage and object of the present invention tocombine the adverse effect caused by excessive photothermal, mechanicalor other type of energy applied to skin or other tissue coupled with atopical or other administration of growth factor(s) or wound healingfactor(s) in order to amplify the natural stimulation of growth orcollagenesis caused by the wound.

The present invention circumvents the problems of the prior art andprovides a system for achieving erythema and mild edema in an upperlayer of skin without the risk of high fluence levels or surface wounds.The invention offer advantages over existing devices by allowing the useof lower fluence levels resulting in faster treatments and less cost.Collagen remodeling is induced by distributing the therapeutic energyover a series of more benign treatments spaced weeks apart. The collagenremodeling is further enhanced by the use of a transforming growthfactor which accelerates the wound healing response. Th growth factor isapplied topically in a media which will act on the skin.

Numerous other advantages and features of the present invention willbecome readily apparent from the following detailed description of theinvention and the embodiments thereof, from the claims and from theaccompanying drawings.

SUMMARY OF THE PRESENT INVENTION

The present invention is a method and apparatus for skin or other tissuetreatment, using a source of thermal energy, which may beelectromagnetic radiation, electrical current, or ultrasonic energy, tocause minimal-invasive thermally-mediated effects in skin or othertissue leading to a wound-healing response, in conjunction with topicalagents which accelerate collagenesis in response to wound healing. Thedosage and time period of application are adjusted to prevent externalor surface tissue damage.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-section view of typical skin tissue.

FIG. 2 is a graph demonstrating the temperature gradient through aportion of the skin as a function of both the wavelength of incidentlaser energy and the depth of laser radiation penetration.

FIG. 3 is a schematic view of a microscope mounted scanner for atemperature controlled collagen shrinkage device used in the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The description that follows is presented to enable one skilled in theart to make and use the present invention, and is provided in thecontext of a particular application and its requirements. Variousmodifications to the disclosed embodiments will be apparent to thoseskilled in the art, and the general principals discussed below may beapplied to other embodiments and applications without departing from thescope and spirit of the invention. Therefore, the invention is notintended to be limited to the embodiments disclosed, but the inventionis to be given the largest possible scope which is consistent with theprincipals and features described herein.

It will be understood that while numerous preferred embodiments of thepresent invention are presented herein, numerous of the individualelements and functional aspects of the embodiments are similar.Therefore, it will be understood that structural elements of thenumerous apparatus disclosed herein having similar or identical functionmay have like reference numerals associated therewith.

Definitions

An “absorption coefficient” of a substance is a measure of the fractionof incident light that is absorbed when light is passed through thesubstance. The absorption coefficient (typically in units of cm⁻¹)varies with the nature of the absorbing substance and with thewavelength of the light.

“Collagen” as used herein refers to any of the several types ofcollagen.

Collagen biosynthesis is said to be “inhibited” when cells treated withthe claimed methods secrete collagen at a rate that is less than about70% of that of untreated cells. Preferably, treated cells secretecollagen at a rate that is less than about 50%, and more preferably lessthan about 30% of the rate at which untreated cells secrete collagen.

Collagen biosynthesis is said to be ‘stimulated’ when cells treated withthe claimed methods secrete collagen at a rate that is greater thanabout 110% of the rate at which untreated cells synthesize collagen.Preferably, treated cells secrete collagen at a rate that is about 150%,and more preferably greater than about 200% greater than that ofuntreated cells.

“Monochromatic” light is of one wavelength or a narrow range ofwavelengths. If the wavelength is in the visible range, monochromaticlight will be of a single color. As used herein, “monochromatic” refersto light that has a bandwidth of less than about 100 nm. Morepreferably, the bandwidth will be less than about 10 nm, and mostpreferably less than about 1 nm.

“Non-coherent light energy” is light that is non-laser. Unlike laserlight, which is characterized by having its photon wave motions inphase, the wave motions of the photons that make up non-coherent lightare in a randomly occurring phase order or are otherwise out of phase.

A “wound” as used herein, refers to any damage to any tissue in a livingorganism. The tissue may be an internal tissue, such as the stomachlining or a bone, or an external tissue, such as the skin. As such, awound may include, but is not limited to, a gastrointestinal tractulcer, a broken bone, a neoplasia, and cut or abraded skin. A wound maybe in a soft tissue, such as the spleen, or in a hard tissue, such asbone. The wound may have been caused by any agent, including traumaticinjury, infection or surgical intervention.

A “growth factor” as used herein, includes any soluble factor thatregulates or mediates cell proliferation, cell differentiation, tissueregeneration, cell attraction, wound repair and/or any developmental orproliferative process. The growth factor may be produced by anyappropriate means including extraction from natural sources, productionthrough synthetic chemistry, production through the use of recombinantDNA techniques and any other techniques, including virally inactivated,growth factor(s)-rich platelet releasate, which are known to those ofskill in the art. The term growth factor is meant to include anyprecursors, mutants, derivatives, or other forms thereof which possesssimilar biological activity(ies), or a subset thereof, to those of thegrowth factor from which it is derived or otherwise related.

FIG. 1 is a cross-section view of typical skin tissue. The uppermostlayer 98 of typical skin tissue is composed of dead cells which form atough, horny protective coating. A thin outer layer, the epidermis 100and a thicker inner layer, the dermis 102. Intertwining S-like fingershaped portions 104 are at the interface between the epidermal papillarylayer 106 and the dermal papillary layer 108, and extend downward.Beneath the dermis is the subcutaneous tissue 110, which often containsa significant amount of fat. It is the dermis layer which contains themajor part of the connective collagen which is to be shrunk, in apreferred embodiment at an approximate target depth of between about 100and 300 microns, according to the method of the present invention,though viable collagen connective tissue also exists to a certain degreein the lower subcutaneous layer as well. Other structures found intypical skin include hair and an associated follicle 112, sweat orsebaceous glands and associated pores 114, blood vessels 116 and nerves118. Additionally, a pigment layer 120 might be present. It will beunderstood that the drawing is representative of typical skin and thatthe collagen matrix will take different forms in different parts of thebody. For example, in the eyelids and cheeks the dermis and subcutaneouslayers are significantly thinner with less fat than in other areas. Thetarget depth will be a function of the amount of scattering in theparticular skin type and the associated absorption coefficient of thetissue. Furthermore, in some cases the actual target depth willcorrespond to one half the thickness of the subject tissue. For example,the target depth of tissue ½ inch thick might be about ¼ inch below thesurface of the skin.

A. Damage to Tissue

Optimum Wavelength: 1.3-1.4 Microns

Methods and devices for modulating collagen biosynthesis are provided.The methods involve focusing non-coherent light energy of apredetermined wavelength to a target site where collagen biosynthesiscan potentially occur. Depending upon the particular wavelengthemployed, collagen biosynthesis is either inhibited or stimulated.Generally, wavelengths in the red and near-infrared portion of theelectromagnetic spectrum stimulate collagen biosynthesis, while longerwavelengths inhibit collagen biosynthesis.

In a preferred embodiment, to inhibit collagen biosynthesis, lightenergy of a wavelength greater than about 1.0 μm, preferably about 1.06μm, is delivered to the target site for a time period sufficient toaccomplish the inhibition. In a preferred embodiment, stimulation ofcollagen biosynthesis occurs when light energy at 640 nm or 900 nm isdelivered to a target site for a time period sufficient to accomplishthe stimulation.

The optimal wavelength within these ranges is influenced by whether thelight energy must pass through overlying tissue before reaching thetarget site. In such cases where the target site is shielded by othertissue, the light energy is transmitted through the shielding tissue andfocused on the target site so that the desired energy level is obtainedat the target site. Because transmission of light through tissue ishighly wavelength specific, one should choose a wavelength that is nothighly absorbed by overlying tissue.

To modulate collagen biosynthesis, an amount of light energy of anappropriate predetermined wavelength is delivered to the target sitethat is sufficient to have the desired stimulatory or inhibitory effect.The amount of energy delivered to a target site is a function of severalfactors, including the output of the light source, the energy flux atthe target site as determined by the source output and the degree offocusing achieved by the light delivery apparatus, and the time periodfor which the target site is exposed to the light energy. Anotherfactor, discussed below, is the nature of any tissue overlying thetarget site.

The appropriate combinations of energy flux and time period for adesired effect on collagen biosynthesis can be determined empirically.For example, one can determine the effect on collagen biosynthesis ofirradiating cells growing in tissue, preferably in monolayers, withlight energy of a given wavelength, energy flux, and time period.

In general, the desired energy density delivered to the target site isbetween about 1.0×10³ and 1.6×10³ Joules cm⁻². Preferably, the energydensity at the target site is about 1.1×10³ Joules cm⁻². For mostapplications, the amount of energy delivered to the target site shouldbe sufficient to modulate collagen

biosynthesis, but should not be so great as to cause a significantdecrease in cell proliferation. For example, 1.7×10³ Joules cm⁻² of 1064nm laser light is known to inhibit fibroblast proliferation. Thus, anenergy that is between about 1.1×10³ and about 1.7×10³ Joules cm⁻² ispreferred.

To achieve the desired energy density, the light energy is delivered tothe target site for a sufficient time period. The time period necessarydepends on the energy flux delivered to the target site by the lightdelivery apparatus. The light can be delivered as a single pulse or as amultiplicity of pulses. Often, the use of short pulses is preferred, asthe shorter pulses cause less undesirable heating of the tissuessurrounding the target site than does a single pulse of longer duration.Preferably, a higher-power shorter-duration pulse is used, rather than alow-power long-duration pulse. Typical pulse durations are between about0.01 and 1.0 seconds, most preferably about 0.1 seconds.

Light Delivery Apparatus

Many types of non-laser light sources are suitable for producing thenoncoherent light that is used in the methods and apparatus of thepresent invention. For example, one can employ polychromatic lightsources such as heated lamp filaments or gas filled vacuum tubes.Commercially available light sources are discussed in, for example,LaRocca, A., “Artificial Sources,” In Handbook of Optics, Vol. 1, Ch.10, Bass et al., eds., McGraw-Hill, New York, 1995, pp. 10.3-10.50, andreferences cited therein.

If a polychromatic light source is used, the light energy is preferablymade monochromatic or nearly monochromatic by suitable methods known tothose of skill in the art. For example, one can direct the polychromaticlight through a filter or a series of filters that transmits only lightof the desired wavelength or range of wavelengths. Suitable filters aredescribed in, for example, Dobrowolski, J. A., “Optical Properties ofFilms and Coatings,” In Handbook of Optics, Vol. 1, Ch. 42, Bass et al.,eds., McGraw-Hill, New York, 1995, pp. 42.3-42.130, and references citedtherein. Bandpass filters are reviewed, for example, in Macleod, H. A.,7hin film Optical E7Iters, McGraw-Hill, New York, 1986;‘Metal-dielectric Interference Filters,” in Physics of 7hin Films, Hasset al., eds., Academic Press, New York, 1977, vol. 9, pp. 73-144; Barr,“The Design and Construction of Evaporated Multilayer Filters for Use inSolar Radiation Technology,” in Advances in Geophysics, Drummond, ed.,Academic Press, New York, 1970, pp. 391-412).

In a preferred embodiment, a monochromatic or nearly monochromatic lightsource is used. By choosing a light source that emits monochromatic ornearly monochromatic light, the need to filter or focus the light to thedesired wavelength is eliminated. Several types of monochromatic ornearly monochromatic light source are known to those of skill in theart. See, e.g., LaRocca, supra., for types and sources of monochromaticlight sources.

Light-emitting diodes (LEDs) are a preferred light source for use in theclaimed invention. LEDs are described, for example, in Haitz et al.,“Light-Emitting Diodes,” In Handbook of Optics, Vol. 1, Ch. 12, Bass,M., ed., McGraw-Hill, New York, pp. 12.1-12.39. Both surface and edgeemitters are commercially available, in continuous and pulse-operatedmodes. Commercially available LEDs that are useful in the claimedmethods emit wavelengths of 830, 904, 1060, 1300, and 1550 nm. Inpreferred embodiments of the present invention, the 830 and 904 nm LEDsare useful for stimulating collagen biosynthesis, while in otherpreferred embodiments of the present invention, the 1060, 1300, and 1550nm LEDs are appropriate for inhibition.

Light energy used in the claimed methods is preferably collimated, inaddition to being of a predetermined wavelength or range of wavelengths.Collimation can be achieved by any of several methods known to those ofskill in the art. For example, passing light through fiber optics ofvarious core diameters will achieve collimation. Suitable fiber opticinstrumentation is available from EG&G Opto-Electronics of Salem, Mass.Optical fibers are described, for example, in Brown, T. G., “OpticalFibers and Fiber-Optic Communications,” In Handbook of Optics, Vol. U,Ch. 10, Bass, M., ed., McGraw-Hill, New York, pp. 10.1 et seq.

The light energy is focused to the target site as a spot having adiameter that is appropriate for the particular treatment beingundertaken. Where inhibition of collagen biosynthesis in a relativelysmall area is used, the light is focused to a correspondingly small spotat the target site. Typically, the light energy is focused to a spotwith a diameter in the range of about 0.25 to about 2.0 millimeters. Thefocusing step also concentrates the light to an energy flux that issufficient to achieve the desired inhibition when delivered to thetarget site for an appropriate period of time.

Methods for focusing light to achieve a desired energy flux and spotdiameter are known to those of skill in the art. For example, a focusinglens made of glass, silica, or refractory material such as diamond orsapphire is commonly employed. In a preferred embodiment, the focusinglens directs the non-coherent light energy to an optical fiber of anappropriate core diameter and composition. For example, a 100 μmdiameter low-OH silica optic fiber is appropriate. A fiber that producesa relatively low amount of transmission loss is preferred, preferablyless than about 15% loss over a length of up to ten meters. The fiber istypically mounted in a shaft for delivery of the non-coherent lightenergy to the tissue. The output end of the shaft is preferably fittedwith an output tip that can dir maintaining the delivery end of thefiber a desired distance away from the tissue. This distance can bevaried by substituting a longer or shorter output tip, or by slidablyadjusting the position of the output tip on the shaft.

For some applications, it is desirable to use an output tip that directsthe noncoherent focused light out of its side, rather than through theend of the fiber. Means for accomplishing this are known to those ofskill in the art. For example, U.S. Pat. No. 5,129,895 describes the useof a reflecting surface at the end of the fiber combined with lensaction on the fiber side.

The invention also provides an apparatus for modulating collagenbiosynthesis according to the methods described herein. The apparatuscomprises a source of noncoherent light energy, a means for collimatingthe light energy generated by the light source, and a means for focusingthe collimated light energy to a target site. The apparatus deliverssufficient light energy to the target site to modulate collagenbiosynthesis.

Therapeutic Applications

The claimed methods for modulating collagen biosynthesis are useful intreating many conditions. Depending upon the condition being treated,either inhibition or stimulation of collagen biosynthesis may bedesired.

The invention also provides methods for stimulating collagenbiosynthesis. These methods are also useful in the clinical setting. Forexample, stimulation of collagen biosynthesis is often desirable in theearly stages of wound healing. The procedures employed are similar tothose used for inhibiting collagen biosynthesis, except for thewavelength of light delivered to the target site. To stimulate collagenbiosynthesis, one delivers light in the red or near-infrared range ofthe electromagnetic spectrum to the target site. For example, lightenergy at 640 nm or 900 nm stimulates collagen biosynthesis whendelivered to a target site at specific energy densities and durations.

To enhance wound healing, collimated fight energy of an appropriatewavelength is delivered to the wound at an energy density sufficient tostimulate collagen biosynthesis. The light energy can be delivered as asingle pulse, or more preferably, as a series of short pulses. The useof short pulses reduces the likelihood of undesired heating of thetissue. Preferably, the light energy delivered is sufficient tostimulate collagen biosynthesis, but is insufficient to inhibit cellproliferation.

FIG. 2 is a graph demonstrating the temperature gradient through aportion of the skin as a function of both the wavelength of incidentlaser energy and the depth of laser radiation penetration. No externalcooling is used. The graph demonstrates a change in temperature (ΔT) ofabout 60 degrees Celsius and all curves are shown for the time point 1millisecond following exposure to the laser energy. The graph showsthree lines corresponding to laser wavelengths of 10.6 microns, 1.3-1.4microns and 1.06 microns.

The present invention utilizes laser energy having a wavelength betweenabout 1 and about 12 microns, more preferably between about 1.2 andabout 1.8 microns, and more preferably about 1.3-1.4 microns. This typeof laser energy is most frequently produced by a Nd:YAG, Nd:YAP orNd:YALO-type laser. A laser operating at these wavelengths may eitherhave a high repetition pulse rate or operate in a continuous wave mode.This laser has been investigated in the medical community as a generalsurgical and tissue welding device, but has not been used for collagentissue shrinkage in the past. Indeed, the prior art teaches away fromthe use of laser energy at 1.3-1.4 microns for shrinking human collagen.

The Nd:YAG, Nd:YAP and Nd:YALO-type lasers are sources of coherentenergy. This wavelength of 1.3-1.4 microns is absorbed relatively wellby water, and as a result is attractive for tissue interaction. It isalso easily transmitted through a fiber optic delivery system as opposedto the rigid articulated arm required for the CO₂ laser. Very precisemethods of controlling laser systems and optically filtering producedlight currently exist. By selecting the appropriate combination ofresonance optics and/or anti-reflection coatings, wavelengths in therange of 1.3-1.4 microns and even 1.32-1.34 microns can be produced.

FIG. 3 is a schematic view of a microscope mounted scanner for atemperature controlled collagen shrinkage device used in the presentinvention. In this view, a laser console 60 is installed adjacent afloor-mounted microscope 62. A fiber optic cable 64 conducts laserenergy from the laser source to the scanner 66. A laser deliveryattachment 68 may be necessary to conduct the laser energy in anappropriate beam pattern and focus. In this embodiment of the invention,servo feedback 70 signals are also conducted along the fiber optic backto the laser console. The servo feedback signals could also be directedback to the laser console via an additional fiber optic or other wiringor cabling. This servo feedback may comprise thermal or optical dataobtained via external sensors or via internal systems, such as afiber-tip protection system which attenuates the laser energytransmitted, to provide control in operation and to prevent thermalrunaway in the laser delivery device. Thus, a thermal feedbackcontroller 72 will regulate the laser energy being transmitted. Thiscontroller can comprise an analog or digital PI, PD or PID-typecontroller, a microprocessor and set of operating instructions, or anyother controller known to those skilled in the art. Other preferredembodiments can also be provided with additional features. For example,the surgeon or technician operating the laser could also manipulate anenergy adjust knob 74, a calibration knob 76 and a footpedal 78. Thus,in a preferred embodiment, a very accurately adjustable system isprovided which allows a surgeon to deliver laser energy via a computercontrolled scanning device, according to instructions given by thesurgeon or an observer inspecting the region of the skin where collagenis to be shrunk through a very accurate microscope. Once a region to betreated is located, the scanner can deliver a very precise,predetermined amount of laser energy, in precisely chosen, predeterminedregions of the skin over specific, predetermined periods of time.

In a preferred embodiment, the invention utilizes an Nd:YAG laser at1320 nm wavelength, (such as the CoolTouch 130, CoolTouch Corp., Auburn,Calif.) as the source of treatment energy. At 1320 nm the absorptiondepth in tissue is such that energy is deposited throughout the upperdermis, with most absorption in the epidermis and upper dermis, a regionincluding the top 200 to 400 microns of tissue. The energy falls offapproximately exponentially with the highest level of absorbed energy inthe epidermis. Optical heating of skin follows exposure to the laserenergy. If the time of exposure to the laser is very short compared tothe time required for heat to diffuse out of the area exposed, thethermal relaxation time, than the temperature rise at any depth in theexposed tissue will be proportional to the energy absorbed at thatdepth. However, if the pulse width is comparable or longer to thethermal relaxation time of the exposed tissue than profile oftemperature rise will not be as steep. Conduction of thermal energyoccurs at a rate proportional to the temperature gradient in the exposedtissue. Lengthening the exposure time will reduce the maximumtemperature rise in exposed tissue.

For example at 1.3 microns the laser pulse width may be set to 30milliseconds and fluence to less than 30 joules per square centimeter.This prevents excessive heat build up in the epidermis, which isapproximately the top 100 microns in skin. The papillary dermis can thenbe heated to a therapeutic level without damage to the epidermis. Theepidermis will reach a temperature higher than but close to that of thepapillary dermis.

The epidermis is more resilient in handling extremes of temperature thanmost other tissue in the human body. It is therefore possible to treatthe papillary dermis in conjunction with the epidermis without scarringor blistering, by treating both layers with laser energy and allowing along enough exposure time such that the thermal gradient between theepidermis and underlying layers remains low. In this way the underlyinglayers can be treated without thermal damage to the epidermis.

A wavelength of 1.3 microns is used in this embodiment to treat themiddle layers of skin. Other wavelengths such as 1.45 or 2.1 microns mayby used to treat more superficial layers of skin by this method. Visiblelight lasers, intense pulsed light sources, energy delivery devices suchas electrical generators, ultrasonic transducers, and microdermabrasiondevices may also be used to initiate a wound healing response withoutsignificant surface wounding. The use of growth factors in conjunctionwith these devices allows for more superficial treatments and improvedresponse.

In one embodiment the invention utilizes an Nd:YAG laser at 1320 nmwavelength, (such as the CoolTouch 130, CoolTouch Corp., Auburn Calif.)as the source of treatment energy. At 1320 nm the absorption depth intissue is such that energy is deposited throughout the upper dermis,with most absorption in the epidermis and upper dermis, a regionincluding the top 200 to 400 microns of tissue. The energy falls offapproximately exponentially with the highest level of absorbed energy inthe epidermis. Optical heating of skin follows exposure to the laserenergy. If the time of exposure to the laser is very short compared tothe time required for heat to diffuse out of the area exposed, thethermal relaxation time, than the temperature rise at any depth in theexposed tissue will be proportional to the energy absorbed at thatdepth. However, if the pulse width is comparable or longer to thethermal relaxation time of the exposed tissue than profile oftemperature rise will not be as steep. Conduction of thermal energyoccurs at a rate proportional to the temperature gradient in the exposedtissue. Lengthening the exposure time will reduce the maximumtemperature rise in exposed tissue.

The present invention also incorporates herein by specific reference, intheir entireties, the following issued U.S. patents:

U.S. Pat. No. 5,885,274 issued Mar. 3, 1999 titled FLASH LAMP FORDERMATOLOGICAL TREATMENT, U.S. Pat. No. 5,968,034 issued Oct. 19, 1999titled PULSED FILAMENT LAMP FOR DERMATOLOGICAL TREATMENT, U.S. Pat. No.5,820,626 issued Oct. 13, 1998 titled COOLING LASER HANDPIECE WITHREFILLABLE COOLANT RESERVOIR,U.S. Pat. No. 5,976,123 issued Nov. 2, 1999titled HEART STABILIZATION, U.S. Pat. No. 6,273,885 issued Aug. 14, 2001titled HANDHELD PHOTOEPILATION DEVICE AND METHOD.

The present invention also incorporates herein by specific reference, intheir entireties, the following pending U.S. patent applications:application Ser. No. 09/185,490 filed Nov. 3, 1998 titled SUBSURFACEHEATING OF TISSUE, application Ser. No. 09/364,275 filed Jul. 29, 1999titled THERMAL QUENCHING OF TISSUE.

B. Wound Healing and Growth Factors

When a tissue is injured, polypeptide growth factors, which exhibit anarray of biological activities, are released into the wound where theyplay a crucial role in healing (see, e.g., Hormonal Proteins andPeptides (Li, C. H., ed.) Volume 7, Academic Press, Inc., New York, N.Y.pp. 231-277 (1979) and Brunt et al., Biotechnology 6:25-30 (1988)).These activities include recruiting cells, such as leukocytes andfibroblasts, into the injured area, and inducing cell proliferation anddifferentiation. Growth factors that may participate in wound healinginclude, but are not limited to: platelet-derived growth factors(PDGFs); insulin-binding growth factor-1 (IGF-1); insulin-binding growthfactor-2 (IGF-2); epidermal growth factor (EGF); transforming growthfactor-.alpha. (TGF-.alpha.); transforming growth factor-.beta.(TGF-.beta.); platelet factor 4 (PF-4); and heparin binding growthfactors one and two (HBGF-1 and HBGF-2, respectively).

PDGFs are stored in the alpha granules of circulating platelets and arereleased at wound sites during blood clotting (see, e.g., Lynch et al.,J. Clin. Invest. 84:640-646 (1989)). PDGFs include: PDGF; plateletderived angiogenesis factor (PDAF); TGF-.beta.; and PF4, which is achemoattractant for neutrophils (Knighton et al., in Growth Factors andOther Aspects of Wound Healing: Biological and Clinical Implications,Alan R. Liss, Inc., New York, N.Y., pp. 319-329 (1988)). PDGF is amitogen, chemoattractant and a stimulator of protein synthesis in cellsof mesenchymal origin, including fibroblasts and smooth muscle cells.PDGF is also a nonmitogenic chemoattractant for endothelial cells (see,for example, Adelmann-Grill et al., Eur. J. Cell Biol. 51:322-326(1990)).

IGF-1 acts in combination with PDGF to promote mitogenesis and proteinsynthesis in mesenchymal cells in culture. Application of either PDGF orIGF-1 alone to skin wounds does not enhance healing, but application ofboth factors together appears to promote connective tissue andepithelial tissue growth (Lynch et al., Proc. Natl. Acad. Sci.76:1279-1283 (1987)).

TGF-.beta. is a chemoattractant for macrophages and monocytes. Dependingupon the presence or absence of other growth factors, TGF-.beta. maystimulate or inhibit the growth of many cell types.

Other growth factors, such as EGF, TGF-.alpha., the HBGFs and osteogeninare also important in wound healing. Topical application of EGFaccelerates the rate of healing of partial thickness wounds in humans(Schultz et al., Science 235:350-352 (1987)). Osteogenin, which has beenpurified from demineralized bone, appears to promote bone growth (see,e.g., Luyten et al., J. Biol. Chem. 264:13377 (1989)). In addition,platelet-derived wound healing formula, a platelet extract which is inthe form of a salve or ointment for topical application, has beendescribed (see, e.g., Knighton et al., Ann. Surg. 204:322-330 (1986)).

The heparin binding growth factors (HBGFs), including the fibroblastgrowth factors (FGFs), which include acidic HBGF (aHBGF also known asHBFG-1 or FGF-1) and basic HBGF (bHBGF also known as HBGF-2 or FGF-2),are potent mitogens for cells of mesodermal and neuroectodermallineages, including endothelial cells (see, e.g., Burgess et al., Ann.Rev. Biochem. 58:575-606 (1989)). In addition, HBGF-1 is chemotactic forendothelial cells and astroglial cells. Both HBGF-1 and HBGF-2 bind toheparin, which protects them from proteolytic degradation. The array ofbiological activities exhibited by the HBGFs suggests that they play animportant role in wound healing.

Basic fibroblast growth factor (FGF-2) is a potent stimulator ofangiogenesis and the migration and proliferation of fibroblasts (see,for example, Gospodarowicz et al., Mol. Cell. Endocinol. 46:187-204(1986) and Gospodarowicz et al., Endo. Rev. 8:95-114 (1985)). Acidicfibroblast growth factor (FGF-1) has been shown to be a potentangiogenic factor for endothelial cells (Burgess et al., supra, 1989).Other FGF's may be chemotactic for fibroblasts. Growth factors are,therefore, potentially useful for specifically promoting wound healingand tissue repair.

“HBGF-1,” which is also known to those of skill in the art byalternative names, such as endothelial cell growth factor (ECGF) andFGF-1, as used herein, refers to any biologically active form of HBGF-1,including HBGF-1.beta., which is the precursor of HBGF-1.alpha. andother truncated forms, such as FGF. U.S. Pat. No. 4,868,113 to Jaye etal., herein incorporated by reference, sets forth the amino acidsequences of each form of HBGF. HBGF-1 thus includes any biologicallyactive peptide, including precursors, truncated or other modified forms,or mutants thereof that exhibit the biological activities, or a subsetthereof, of HBGF-1.

Other growth factors may also be known to those of skill in the art byalternative nomenclature. Accordingly, reference herein to a particulargrowth factor by one name also includes any other names by which thefactor is known to those of skill in the art and also includes anybiologically active derivatives or precursors, truncated mutant, orotherwise modified forms thereof.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which the present invention belongs. Although any methods andmaterials similar or equivalent to those described can be used in thepractice or testing of the present invention, the preferred methods andmaterials are now described. All publications and patent documentsreferenced in the present invention are incorporated herein byreference.

While the principles of the invention have been made clear inillustrative embodiments, there will be immediately obvious to thoseskilled in the art many modifications of structure, arrangement,proportions, the elements, materials, and components used in thepractice of the invention, and otherwise, which are particularly adaptedto specific environments and operative requirements without departingfrom those principles. The appended claims are intended to cover andembrace any and all such modifications, with the limits only of the truepurview, spirit and scope of the invention.

1. A method for treatment of skin comprising: Treating a subsurfacelayer of un-damaged skin with a source of electromagnetic energysufficient to cause stimulation of collagen biosynthesis without thermaldamage to the epidermis, in conjunction with using a thermal servofeedback control system to regulate the delivery of electromagneticenergy, thereby achieving improved collagenesis in the skin.
 2. Themethod of claim 1 further comprising the step of controllably deliveringpulsed cryogen spray to the skin to prevent overheating of the skin. 3.The method of claim 1 wherein the treatment is repeated serially withmore than one day between any successive treatments.
 4. A method fortreatment of acne scars in skin, comprising: Treating contiguoussubsurface and surface layers of the skin with a source ofelectromagnetic energy in order to stimulate collagen biosynthesis inthe skin without thermal damage to the epidermis, in conjunction withusing a thermal servo feedback control system to regulate the deliveryof electromagnetic energy, thereby improving the appearance of the acnescars.
 5. The method of claim 4 further comprising the step ofcontrollably delivering pulsed cryogen spray to the skin to preventoverheating of the skin.
 6. A method for treatment of photodamaged skin,comprising: Treating the layer of skin with a source of electromagneticenergy which stimulates biosynthesis of collagen without thermal damageto the epidermis, in conjunction with using a thermal servo feedbackcontrol system to regulate the delivery of electromagnetic energy,thereby improving the appearance of the photodamaged skin.
 7. The methodof claim 6 further comprising the step of controllably delivering pulsedcryogen spray to the skin to prevent overheating of the skin.
 8. Amethod for treatment of wrinkled skin, comprising: Treating the layer ofwrinkled skin with a source of electromagnetic energy which stimulatesbiosynthesis of collagen without thermal damage to the epidermis, inconjunction with using a thermal servo feedback control system toregulate the delivery of electromagnetic energy, thereby improving theappearance of the wrinkled skin.
 9. The method of claim 8 furthercomprising the step of controllably delivering pulsed cryogen spray tothe skin to prevent overheating of the skin.
 10. A system for treatmentof skin, comprising: A source of electromagnetic energy which issufficient to stimulate biosynthesis of collagen in the skin withoutthermal damage to the epidermis; and A thermal servo feedback controlsystem to regulate the delivery of electromagnetic energy, therein,thereby resulting in improved appearance of skin.
 11. The method ofclaim 10 further comprising the step of controllably delivering pulsedcryogen spray to the skin to prevent overheating of the skin.
 12. Amethod for treatment of undamaged tissue comprising the following steps:Causing a subdermal stimulation of collagen biosynthesis without thermaldamage to the epidermis using a source of electromagnetic energy; andUsing a thermal servo feedback control system to regulate the deliveryof electromagnetic energy, such that collagenesis, repair and healingimprovement of tissue is accelerated.
 13. The method of claim 12 furthercomprising the step of controllably delivering pulsed cryogen spray tothe skin to prevent overheating of the skin.
 14. A method for treatingskin disorders with optical energy comprising the step of deliveringoptical energy to the skin and the step of using temperature sensingelements to provide feedback to a controller such that the opticalenergy can be modulated to maintain a predetermined skin temperature toprevent over treatment.
 15. The method of claim 14 further comprisingthe step of controllably delivering pulsed cryogen spray to the skin toprevent overheating of the skin.
 16. A method for treating skin withoptical energy comprising the step of delivering optical energy to theskin and the step of using temperature sensing elements to providefeedback to a controller such that the optical energy can be modulatedto maintain a predetermined skin temperature to prevent over treatment.17. The method of claim 16 further comprising the step of controllablydelivering a pulse of cryogen spray to the skin to prevent overheatingof the skin.